This invention relates to telescope systems. Simple telescope systems typically have an objective imaging assembly and an ocular assembly that together provide a user with a magnified virtual image of a distant object which is upside down and backwards left to right. Objective imaging assemblies are composed of arrangements of either refracting lenses or reflecting mirrors. Objective imaging assemblies provide a real intermediate image of the object which is inverted about both horizontal and vertical axis so that it is upside-down and backwards left to right. Oculars provide a virtual image of the intermediate image with the same orientation as the intermediate image.
More complex telescope systems, known as terrestrial or spotting telescopes, have an erecting system located between the objective and the ocular that inverts the intermediate image about both the horizontal and vertical axes so that the final image appears upright and correct left to right.
Still other telescope systems have offset image convertors, usually comprised of a star diagonal prism or a mirror, for producing the final image in a focal plane that is offset by an angular amount from the focal plane of the intermediate image. The main purpose of these offset image convertors is to provide comfortable viewing for the telescope user when the objective assembly must be aimed in a direction which would otherwise produce uncomfortable viewing. Examples of such use would be astronomical viewing or birdwatching, where looking upward for long periods can cause substantial neck and shoulder fatigue. These offset image convertors generally also invert the intermediate image, but only about one axis. When these convertors are incorporated into a simple telescope, the resulting final image is upright but backwards left to right. When they are used in a terrestrial telescope, the resulting final image is upside-down but correct left to right.
It is desirable to provide an improved telescope system which provides optimum viewing comfort for a wide range of both astronomical and terrestrial uses while always producing an erect final image, upright and correct left to right.
Therefore, it is an object of the present invention to provide an improved telescope system which provides optimum viewing comfort by allowing viewing of the final image along a number of alternative axes depending only on the particular object of interest. It is a further object of this invention to provide an erect final image, upright and correct left to right, under all conditions regardless of which alternative viewing axis is chosen.